United Nations Environment ProgrammeP.O. Box 30552 - 00100 Nairobi, Kenya

Tel.: +254 20 762 1234Fax: +254 20 762 3927

e-mail: yearbook@unep.orgwww.unep.org

www.unep.org

UN

EP YEA

R BOO

K 2011 EM

ERGIN

G ISSUES IN

OU

R GLO

BAL EN

VIRO

NM

ENT

The ocean has become a global repository for much of the waste we produce. Scientists are concerned that plastic debris in the ocean can transport toxic substances which may end up in the food chain, causing potential harm to ecosystems and human health. The Year Book also explores the wider implications of the use of phosphorus in food production. Phosphorus is an essential nutrient whose supply is limited. Since demand for fertilizer in agriculture rocketed in the 20th century, large amounts of phosphorus are flowing into the environment. New perspectives are also emerging on how biodiversity conservation can be integrated in forest management. Forests are receiving increasing attention, not least because of their role in climate change mitigation. Halting loss of forest biodiversity is essential if forests are to adapt to mounting pressures, including climate change and pest outbreaks.

The Year Book’s overview of events and developments during 2010 shows how cutting edge science reveals new opportunities to mitigate climate change while improving air quality. Stimulated by technological innovation and green investments, renewable energy supply is growing rapidly. This and other developments are summarized in key environmental indicators that present the latest data and trends for the global environment.

978-92-807-3101-9DEW/1300/NA

978-92-807-3101-9DEW/1300/NA

United Nations Environment Programme

2011

UYB KOO

E A RN E P

E M E R G I N G I S S U E S IN OUR GLOBAL ENVIRONMENT

The spine needs to be adjusted according to the thickness of the book. If the spine is too narrow, the text might be too small.The text on the spine should then be removed.Check with printer about the black and reversed out text because the Black is made up of 50C 50M 50Y 100K to achieve a strong, solid black.

UNEP YEAR BOOK 201134

Until it was treated with phosphorus fertilizers, soil in Brazil’s Cerrado region was largely agriculturally unproductive. Maize plants grown on phosphorus-treated soil are much taller than control plants like those in the foreground, which did not receive adequate additional phosphorus. Credit: D.M.G. de Sousa

35PHOSPHORUS AND FOOD PRODUCTION

Virtually every living cell requires phosphorus, the 11th mostabundantelementintheEarth’scrust.However,thesoilfromwhichplantsobtainphosphorustypicallycontainsonlysmallamountsofit inareadilyavailableform.Thereisnoknownsubstituteforphosphorus in agriculture. If soils are deficient in phosphorus,foodproductionisrestrictedunlessthisnutrientisaddedintheformoffertilizer.Hence,toincreasetheyieldofplantsgrownforfood,anadequatesupplyofphosphorusisessential.

Farmingpracticesthatarehelpingtofeedbillionsofpeopleinclude the application of phosphorus fertilizers manufacturedfrom phosphate rock, a non­renewable resource usedincreasinglysincetheendofthe19thcentury.Thedependenceof food production on phosphate rock calls for sustainablemanagement practices to ensure its economic viability andavailabilitytofarmers.Whiletherearecommerciallyexploitableamounts of phosphate rock in several countries, those with nodomesticreservescouldbeparticularlyvulnerableinthecaseofglobalshortfalls.

Use of phosphorus in agriculture is associated with severaltypesofpotentialenvironmentalimpacts.Toolittlephosphorus

Phosphorus and Food Production

Authors: Keith Syers (chair), Mateete Bekunda, Dana Cordell, Jessica Corman, Johnny Johnston, Arno Rosemarin and Ignacio Salcedo Science writer: Tim Lougheed

Phosphorus is essential for food production, but its global supply is limited. Better insight is needed into the availability of this non-renewable resource and the environmental consequences associated with its use. Optimizing agricultural practices while exploring innovative approaches to sustainable use can reduce environmental pressures and enhance the long-term supply of this important plant nutrient.

restrictsplantgrowth,leadingtosoilerosion.Phosphorusoverusecan result in losses to surface waters and eutrophication. Moresustainablepractices—suchasbettermanagedfieldapplicationsand enhanced phosphorus recycling—can contribute toimprovementsinproductivityandreduceenvironmentalimpactswhile increasing the life­span of this finite resource. Figure 1shows the phosphorus flows in the environment. Althoughmuch is known about how to locally enhance soil fertility byadding phosphorus, there is a need for a more comprehensiveunderstandingandbetterquantificationoftheglobalpathways.

Scientists are starting to quantify global phosphorus flowsthrough the food production and consumption system. It isestimated that only one­fifth of the phosporus mined in theworld is consumed by humans as food (Schröder et al. 2010).Yet important knowledge gaps remain concerning how muchphosphorus is obtained, how much is used in agricultureand retained in soil, and how much is released to the aquaticenvironmentorlostinfoodwaste.

Supplying a critical nutrientHigh crop yields today depend fundamentally on minedphosphate rock, a significant departure from historical foodproduction methods. When the world population was muchsmaller, farmers could obtain adequate yields by fertilizingsoilwithphosphorusderivedfromhumanandanimalexcreta.Population growth in the 18th and 19th centuries stimulatedfood production, resulting in more rapid depletion of soilnutrients.Farmersthereforebegantouseincreasingamountsofoff­farmsourcesofphosphorus,includingbonemeal,guanoandphosphaterock(Jacob1964).Phosphaterock,whichwascheapand plentiful, became the source that was widely preferred

Phosphorus resources and reservesResourcesareconcentrationsofnaturallyoccurringphosphatematerialinsuchaformoramountthateconomicextractionofaproductiscurrentlyorpotentiallyfeasible.

Reservesarethepartofanidentifiedresourcethatmeetsminimumcriteriarelatedtocurrentminingandproductionpractices,includinggrade,quality,thicknessanddepth,andthatcanbeeconomicallyextractedorproducedatthetimeofthedetermination.Useofthistermdoesnotsignifythatthenecessaryextractionfacilitiesareinplaceorworking.

Source: Adapted from Van Kauwenbergh (2010) and Jasinski (2011)

UNEP YEAR BOOK 201136

Figure 1: Phosphorus flows in the environment. To enhance food production, phosphorus is added to soil in the form of mineral fertilizer or manure. Most of the phosphorus not taken up by plants remains in the soil and can be used in the future. Phosphorus can be transferred to surface water when it is mined or processed, when excess fertilizer is applied to soil, when soil is eroded, or when effluent is discharged from sewage treatment works. Red arrows show the primary direction of the phosphorus flows; yellow arrows the recycling of phosphorus in the crop and soil system and movement towards water bodies; and grey arrows the phosphorus lost through food wastages in landfills.

PHOSPHATE ROCKMINING

FERTILIZERPRODUCTION

LIVESTOCK AND CROP PRODUCTION

HUMAN CONSUMPTION

WASTE MANAGEMENT

FOOD PROCESSING

PHOSPHORUS POOL IN THE SOIL

EROSION LOSSAND RUN-OFF

(Smil 2000) (Figure 2). Farmers also adopted new methods,suchasplantinghigh­yieldingcropvarietiesandthenapplyingnutrients—notably nitrogen, phosphorus and potassium(NPK)—and other inputs such as pesticide (Fresco 2009).Scientificprogresscontinuedinthelasthalfofthe20thcenturywiththeGreenRevolution.Althoughitstavedoffagreatdealofworldhunger in the faceofsignificantpopulationgrowth, theGreenRevolutionhasbeencriticizedforcausingenvironmental

damage by encouraging excessive or inappropriate use offertilizersandotherinputs(IFPRI2002).

Tosustainagriculturalproductivityatcurrentandpredictedfuture levels, it is crucial to determine the full extent of thesupply of this finite resource. Thirty­five countries currentlyproducephosphaterockanditisestimatedthat15othershavepotentially exploitable resources (IFA 2009). Phosphate rock’svaluedependsonvariousfactors,includingphysicalaccessibility,

37PHOSPHORUS AND FOOD PRODUCTION

Figure 2: Global sources of phosphorus fertilizer. Since the mid-1940s, population growth accompanied by greater food demand and urbanization have led to a dramatic increase in the use of mined phosphate rock compared with other sources of phosphorus. Source: Cordell et al. (2009)

Phos

pho

rus

(Mt)

1960 1970 1980 1990 2000 2010195019401930192019101900189018801870

26

8

20

14

Year

Guano

Phosphate rockHuman excreta

Manure

12

24

18

10

22

16

2

6

4

0185018401830182018101800 1860

level of impurities and phosphate content. The known supplyof cheap, high­grade reserves is becoming increasingly limitedwhiledemandcontinues to increase.The remainingamountofcommerciallyviablephosphaterock,particularly the lifetimeofreserves,hasbeenthesubjectofvigorousdebateamongexpertsduringthelastfewyears(Vaccari2009)(Box 1).

New phosphate rock mines have been commissioned inseveral countries, including Australia, Peru and Saudi Arabia,whileundiscovereddepositsarebeingwidelysought,includingin seafloor sediments off the coast of Namibia (Drummond2010, Jung 2010, Jasinski 2010 and 2011). Although estimatesof the extent of known reserves are increasing, the quality ofthese reserves requires further evaluation. If the phosphateconcentration in the rock declines and larger volumes of oreare needed in order to obtain a given amount of phosphorus,productioncostswilllikelyincrease.Suchchangescouldalsoleadto greater energy requirements and more waste in phosphaterock mining. In an open market these factors might well raisethepriceofphosphorus fertilizers, limitingtheiraccessibility tomanyfarmersandhavingnegativeeffectsonyields.Iftheseweretooccur,foodsecuritycouldbethreatenedincountriesthatarehighlydependentonphosphorusimports.

The eradication of hunger and poverty is Goal 1 of theMillenniumDeclaration,adoptedbytheUnitedNationsGeneralAssemblyin2000.A2010reviewofprogresstowardsachievingthe Millennium Development Goals reported that hungerand malnutrition increased between 2007 and 2009, partiallyreversing earlier progress (UNGA 2010). Many of the world’sestimated 925 million undernourished people are small­scalefarmers (IAASTD 2009, FAO 2010). Phosphorus­based fertilizersare often unobtainable by these farmers, whose productivitycouldbeimprovedwithbetteraccesstothisinput(Bureshetal.1997).

Greater appreciation of the role and value of phosphoruscould be the basis for increased co­operation on research anddevelopmenttoacquireamorecomprehensiveunderstandingofthisessentialnutrient—includinghow itcanbestbe recovered,used and recycled to meet future food demand. Researchhas already demonstrated the importance of building up andmaintainingacriticallevelofplant­availablephosphorusinsoiltooptimize plant uptake of this nutrient; anything lower than thislevel would represent a loss of crop yield, and anything higheran unnecessary expense for farmers and a potential cause ofphosphorusrun­offtoreceivingwaters(Syersetal.2008).Good

38 UNEP YEAR BOOK 2011

The extent of global phosphate rock reserves is difficult to ascertain. Knowledge of phosphate rock deposits is evolving, along with technology and the economics of production (IFDC/UNIDO 1998). How long reserves will last depends on their size, quality and rate of use.

Researchers have raised concern about ‘peak phosphorus’, the proposition that economic and energy constraints will set a maximum level for phosphate rock production, which will then decrease as demand for phosphorus increases. Many scientists and industry experts contest the specific assertions that have been made regarding when such a peak is likely to occur. For example, Cordell et al. (2009) estimated that peak production of current reserves (that is, phosphate rock known to be economically available for mining and processing) would occur between 2030 and 2040. That estimate was based on United States Geological Survey (USGS) data for global phosphate reserves (Jasinski 2006, 2007 and 2008). Increasingly experts now consider the extent of these reserves to have been underestimated (Van Kauwenbergh 2010). The most recent

Country

Phosphate rock reserves,

millions of tonnes

Morocco 5700

China 3700

SouthAfrica 1500

Jordan 1500

UnitedStates 1100

Brazil 260

Russia 200

Israel 180

Syria 100

Tunisia 100

Othercountries 1660

Worldtotal(rounded) 16000

Phos

phat

e ro

ck (M

t)

MoroccoChina

United States

Jordan

South Africa

BrazilRussia

Israel

TunisiaEgypt

Syria

Australia

SenegalTogo

Canada

Other countries

5001 000

1 5002 0002 5003 0003 5004 000

50 50051 00051 500

51 000

1 800

2505185230

500 400 230

900

3 700

600

5345082 0

50 000

4 5005 0005 5006 0006 5007 000

Figure 3: Recent estimates of the distribution of world phosphate rock reserves, as reported by the United States Geological Survey (left) and the International Fertilizer Development Center (right). Most potentially viable phosphate rock reserves are concentrated in a few countries. Sources: Jasinski (2010) and Van Kauwenbergh (2010) Note: The United States Geological Survey’s Mineral Commodity Summaries 2011, published on 21 January 2011, revised the USGS estimate of world phosphate rock reserves to 65 billion tonnes. Its revised estimate of Moroccan reserves is 50 billion tonnes, based on information from the Moroccan producer and IFDC. The top ten countries in the 2011 report are Morocco, China (3 700 Mt), Algeria (2 200 Mt), Syria (1 800 Mt), Jordan (1 500 Mt), South Africa (1 500 Mt), the United States (1 400 Mt), Russia (1 300 Mt), Brazil (340 Mt) and Israel (180 Mt). Source: Jasinski (2011)

Box 1: The ‘peak phosphorus’ debate: how long will global phosphate rock reserves last?

USGS estimates have been revised upward (Jasinski 2011). Proponents of the peak phosphorus theory argue that even if the timeline may vary, the fundamental issue, that the supply of cheap and easily accessible phosphorus is ultimately limited, will not change.

A recent report from the International Fertilizer Development Center (IFDC) on reserves and resources provisionally revised the estimate of phosphate rock reserves from the USGS estimate of around 16 billion to approximately 60 billion tonnes (Van Kauwenbergh 2010), which is roughly consistent with the most recent USGS report (Jasinski 2011) (Figure 3). These reserves would last 300 to 400 years at current production rates of 160 to 170 million tonnes per year. Since phosphorus fertilizer production is expected to increase by 2 to 3 per cent per year during the next five years, the life expectancy of reserves could be less than that (Heffer and Prud’homme 2010). The IFDC report also estimates that the world’s overall phosphate resources amount to approximately 290 billion tonnes and potentially as much as 490 billion tonnes (Van Kauwenbergh 2010).

Phosphate rock is the only new source of phosphorus entering the food production chain. The consistency and volume of food production therefore depend on the accessibility of phosphorus to farmers. Given the difficulties of estimating the longevity of phosphate rock reserves and the vital importance of decision-making based on reliable and transparent information concerning world phosphate rock resources and reserves, IFDC recommends establishing an international, multi-disciplinary network to regularly update a definitive database on phosphate rock deposits (Van Kauwenbergh 2010).

39PHOSPHORUS AND FOOD PRODUCTION

Phos

pho

rus

(Mt)

1960 1964 1966 1972 1976 1980 1984 1988 1992 1996 2000 2004 2008 2012 2016

25

10

20

5

15

0

Year

Developing countries forecastDeveloped countries World

Figure 4: Global phosphorus fertilizer consumption. Demand in developed countries reached a plateau and then declined around 1990. It has continued to increase steadily in developing countries. Source: Heffer and Prud’homme (2010)

management practices for fertilizers and agricultural wasteproducts are advocated by many organizations and initiatives,includingtheInternationalPlantNutritionInstituteandtheGlobalPartnershiponNutrientManagement(GPNM2010).

More sustainable use of a finite resourceAlmost90percentofglobalphosphaterockproductionisusedtoproducefoodandanimalfeed(Prud’homme2010).Theneedforincreasedagriculturalproductivitywillcreatehigherdemandfor fertilizer to meet crop requirements by improving suppliesof phosphorus, nitrogen and potassium. The specific amountsrequiredwillvarywithsoiltype.Phosphorusfertilizerconsumptionhasstabilizedinmuchofthedevelopedworld,butitisexpectedtocontinuetoincreasesteadilyindevelopingcountries(Figure 4)(Box 2).Populationgrowthwilldrivemuchofthisdemand,butso will increased consumption of meat and dairy products andthe cultivation of crops for non­food purposes such as biofuelfeedstock(FAO2008,IFA2008,VanVuurenetal.2010).

Global use of fertilizers that contain phosphorus, nitrogenandpotassiumincreasedby600percentbetween1950and2000(IFA2006).Thishelpedtofeedagrowingworldpopulation,butexcessiveorinappropriatefertilizerusehasalsoledtosignificantpollutionproblemsinsomepartsoftheworld.

In the last half­century, the phosphorus concentrations infreshwaterandterrestrialsystemshaveincreasedbyatleast75percentwhiletheestimatedflowofphosphorustotheoceanfromthetotallandareahasrisento22milliontonnesperyear(Bennettetal.2001).Thisamountexceedstheworld’sannualconsumptionof phosphorus fertilizer, estimated at 18 million tonnes in 2007(FAOStat 2009).While much of the phosphorus accumulated interrestrialsystemswouldeventuallybeavailableforplantgrowth,there is no practical way to recover phosphorus lost to aquaticsystems.

In aquatic systems too much phosphorus and othernutrients results in eutrophication, which promotes excessivealgal and aquatic plant growth along with undesirable impactson biodiversity, water quality, fish stocks and the recreational

UNEP YEAR BOOK 201140

valueoftheenvironment.Algalbloomscanincludespeciesthatrelease toxins which are harmful to humans or animals, whiledecomposition of algae can lower dissolved oxygen levels,causing mass mortality among fish (Carpenter et al. 1998, MA2005). Scientists have warned that human­induced nutrientover­enrichment can push aquatic ecosystems beyond naturalthresholds, causing abrupt shifts in ecosystem structure andfunctioning(Rockströmetal.2009).

The estimated annual cost of eutrophication in the UnitedStatesaloneisashighasUS$2.2billion(Doddsetal.2009).Thisproblem isexacerbated incountries’ largeurbancentres,wherephosphorus from excreta and detergents is concentrated inwastewater streams and discharged along with nitrogen andother nutrients. If local authorities do not invest in facilities toremovethesenutrients,theywillbedischargedwithothereffluentinto riversandotherwaterbodies (Van Drechtetal.2009).This

isfrequentlythecaseinthemega­citiesindevelopingcountries,where more than 70 per cent of wastewater enters surface orgroundwateruntreated(Nyenjeetal.2010).

In many parts of the world, traditional nutrient cycles thatwereoncethebasisof local foodproduction,consumptionandwaste management have changed in response to the need toproduce more food in a globalizing world. Over four times asmuch phosphorus flows through the environment than beforephosphorusfertilizerbegantobeusedinagriculture(Smil2002).Soils that receive phosphorus retain a high proportion, but thevariabilityoftheworld’ssoilsmakesthisamountdifficulttoassess,particularly at large scales. Agricultural efficiency—especially intheexpandingareaof livestockmanagement—willbeessentialto optimize phosphorus use, avoid nutrient losses and meetincreasingly strict environmental regulations. For example, theEuropean Union’sWater Framework Directive requires potential

Eighty-two per cent of the world’s 6.8 billion people live in developing regions (UN 2009). Sixteen per cent of the population in these regions is chronically undernourished (UN 2010), which in some regions can largely be linked to soils’ low productive capacity. For example, in Africa nearly three-quarters of farmland is depleted of nutrients, lowering crop yield to one-quarter of the global average (Henao and Baanante 2006). At the same time, more nutrients continue to be removed each year than are added in the form of fertilizer, crop residues and manure.

Nutrient balance studies in the 1990s suggested average annual depletion rates of 22 kg nitrogen (N), 2.5 kg phosphorus (P) and 15 kg potassium (K) per hectare in Africa. Intensively cultivated highlands in East Africa lose an estimated 36 kg N, 5 kg P and 25 kg K per hectare per year, while croplands in the Sahel lose 10 kg N, 2 kg P and 8 kg K per hectare (Smaling et al. 1997). Average annual fertilizer use in Africa is only about 17 kg per hectare, compared, for example, to 96 kg per hectare in Latin America (Figure 5). Even this low rate of consumption is restricted to just a few African countries. Sub-Saharan Africa, excluding South Africa, uses about 5 kilograms of fertilizer per hectare per year, of which less than 30 per cent is phosphorus. These levels are insufficient to balance offtake in crop products.

A combination of high cost and low accessibility prevents many African farmers from acquiring fertilizer. Poor transport, low trade volumes, and lack of local production or distribution capacity result in farm-gate fertilizer prices two to six times higher than the world average. Nevertheless, fertilizer is needed to achieve adequate sustainable crop yields. The Africa Fertilizer Summit (2006) concluded that a lasting solution requires policies to sustain robust distribution networks, including adequate credit sources, retail outlets and transportation, as well as the transfer of technology and knowledge for efficient fertilizer use.

Figure 5: Regional disparities in the application of fertilizers containing nitrogen, phosphorus and potassium. Source: IFA (2009)

5

96

1710

196

85

Sub-SaharanAfrica minusSouth Africa

Africa Latin America

NorthAmerica

East and

Southeast Asia

0

50

100

150

200

Kilo

gram

s fe

rtili

zer p

er h

ecta

re

Sub-SaharanAfrica

Box 2: Phosphorus use in African agriculture

A more sustainable strategy would include integrated soil nutrient management to make the most of organic sources of phosphorus, such as crop residues, animal manure and food waste, combined with more judicious use of mineral phosphorus fertilizers (Alley and Vanlauwe 2009). This would result in multiple environmental benefits, including erosion control. Run-off and erosion combined are responsible for 48 and 40 per cent of phosphorus losses in intensively cultivated highland areas and in parts of the Sahel, respectively (Smaling et al. 1997).

41PHOSPHORUS AND FOOD PRODUCTION

pollutantstoberemovedfromwastewaterpriortodisposalintosurfacewater.Sustainablelandmanagementisimportantfortheprevention of phosphorus loss to water bodies resulting fromsoilerosion.Improvedtechnologiestoremoveimpuritiessuchasheavy metals from fertilizer products would also minimize theirtransfertoagriculturalsoilsorsurfacewaters.

Usingphosphaterockmoresustainablywouldhelpensureitslong­termeconomicviabilityandtheavailabilityofphosphorusto farmers. Because phosphorus flows through the global foodsystem,thereareoptionsforenhancingefficiencyateachstageofthevaluechain.They include lengtheningthe lifeofreservesthroughimprovementsinmining(Box 3),infertilizerproductionandinfertilizeruseefficiency.Recyclingphosphorusfromexcretaorotherorganicwastesalsopresentsan importantopportunity

Box 3: Improving the sustainability of phosphorus mining

The environmental performance of the fertilizer raw material industry has improved in recent decades, with a greater focus on sustainability in the mining sector. New management systems have been responsible for improved environmental performance, which also yields economic benefits. Increasing phosphorus recovery during mining operations can extend the life expectancy of reserves (Prud’homme 2010).

The area affected by surface mining operations varies with ore-body geometry and thickness. The phosphate content of the ore is upgraded by concentration, or ‘beneficiation’. This process removes contaminants such as clay and other fine particles, organic matter, and siliceous and iron-bearing minerals (UNEP/IFA 2001). Such materials are usually removed by crushing/grinding, scrubbing, water washing and screening. They end up in water bodies, mined-out areas or specially designed ponds.

As with many mining activities, the extraction and beneficiation of phosphate rock has potential negative environmental impacts, including damage to the landscape, excessive water consumption, water contamination and air pollution. These impacts are localized and are mostly limited to the mining site (UNEP/IFA 2001). A range of landscaping practices are used to minimize disturbance and accelerate the re-establishment of vegetation, while wastes are confined to a specific area, providing a high degree of management control.

Work is currently under way to recycle process water, reclaim fines, and treat the waste stream to increase the recovery rate. However, information on phosphorus recovery in mining and ore beneficiation is lacking. Reported rates vary widely, with values ranging between 41 and 95 per cent (Prud’homme 2010, Van Kauwenbergh 2010).

Eutrophication of Lake Winnipeg in Manitoba, Canada. Ongoing efforts to improve the lake’s health include reducing nutrient inflow from wastewater, eliminating fertilizer use in buffer zones, and reducing phosphorus content in household detergents. Credit: Lori Volkart

torecoverthisnutrient.Giventhediversityofphosphorus­relatedissues, an environmentally integrated set of policy options andtechnicalmeasuresisrequiredtoensuremoresustainableuseofthisessentialresource.

Soil erosion is a natural process significantly accelerated byhumanactivity,particularlylandusechangessuchasdeforestation.Overgrazingorremovalofvegetationleavesthesoilunprotectedandvulnerabletotheeffectsofrain.Soilsareparticularlypronetoerosionintropicalandsubtropicalregions,whererainfallisusuallyhigherandmoreintense.Ratesoferosionvarywiththetypeofsoilandlandscape.

Anumberofmeasurescanbetakentoenhancetheefficiencyof phosphorus use and reduce phosphorus losses, such aseffective land management to help reduce losses due to soilerosion(Box 4).

UNEP YEAR BOOK 201142

Open-cast mining of phosphate rock in Togo. Most of the world’s phosphate rock is extracted from open pits, as shown here, or from large-scale mines equipped with drag lines or shovel/excavator systems. Credit: Alexandra Pugachevsky

Box 4: Managing soil erosion to minimize phosphorus losses

Since plant nutrients are concentrated in the topsoil, removal of surface soil through erosion can greatly reduce soil productivity. Siltation and eutrophication also damage the aquatic environment. Thus, protecting topsoil from soil erosion maintains soil productivity and conserves water quality.

Measured rates of erosion and sediment transport vary. Topsoil removal rates of 0.47 tonnes per hectare per year have been measured in Africa, compared with rates almost four times as high in Asia (El Swaify et al. 1982). Due to the cost of making measurements, erosion simulation models have been developed. However, these models often provide different results when applied at different spatial scales.

Some 75 to 90 per cent of the phosphorus lost in surface run-off from cropped land is associated with soil particles (Sharpley and Rekolainen 1997). In Africa total annual phosphorus removal by all pathways is

estimated at 2.5 kilograms per hectare, while phosphorus loss due to erosion and run-off is approximately 1 kilogram per hectare per year (Smaling et al. 1997).

Several well-recognized practices can minimize soil erosion, such as contour ploughing carried out parallel to the land’s contours rather than up or down slopes, and contour planting of hedgerows on steep land. Since it is vegetation cover that principally determines the extent of soil loss by erosion, the long-term solution to control erosion rates is through vegetation protection, including use of mulches, cover crops, and fertility-enhancing systems on low-fertility soil (Stocking 1984). These practices have the potential to be more widely adopted in the developing world, although they are limited by lack of land tenure, the costs of adopting them, limited extension support and other socio-economic factors. Improved farmer education is an important starting point.

43PHOSPHORUS AND FOOD PRODUCTION

Major gains can be made through improving plantnutrient management and recycling phosphorus from wastestreams (Syers et al. 2008, Gilbert 2009, Van Vuuren et al.2010). Technological innovations in waste management candramatically lower the amount of phosphorus making its wayinto the aquatic environment (Box 5). Such improvementssometimes produce co­benefits such as energy generationfrombiogas(VanVuurenetal.2010).Recyclingsewagesludge

is another option, although there are some health concernsas sludge may contain high concentrations of heavy metals,pathogensandothercontaminants.

Some European countries are already formulating targetsforphosphorusrecycling.Forexample,Swedenaimstorecycle60percentofthephosphorusinmunicipalwastewaterby2015(SwedishEnvironmentalProtectionAgency2010).

Technological innovation has resulted in the development of a pig able to digest phytate. This reduces the need to provide a phosphorus supplement, much of which is excreted. Approval by the Canadian government in early 2010 allowed farmers to begin raising the Enviropig, a significant step towards enabling its processing and sale as food. Credit: University of Guelph

For centuries, animal and human excreta have been added to farmland to supply nutrients for growing crops. Farmers in most parts of the world still consider animal manure a valuable soil amendment. To recover nutrients, including the phosphorus in human excreta, a wide range of technologies are being developed, ranging from low-cost, small-scale systems to expensive high-technology ones.

‘Ecological sanitation’ recovery systems for human excreta are designed to close nutrient and water cycles. For example, nutrient recycling from human waste can be achieved using urine-diverting dry toilets (Morgan 2007). Such on-site systems are particularly appropriate in rural and peri-urban areas, where households are not connected to sewerage or farmers do not have access to—or cannot afford—chemical fertilizers (Rosemarin et al. 2008). Trials in villages in Niger by Dagerskog and Bonzi (2010) found that an average rural family of nine persons excreted the equivalent of chemical fertilizer worth about US$80 per year. The urine component produced comparable or 10 to 20 per cent higher yields of sorghum and millet, compared to the same amount of nutrients applied as chemical fertilizer.

Interest in recycling phosphorus and other nutrients from sanitation systems has been increasing for several years (Esrey et al. 2001). Responding to this interest, the World Health Organization has developed guidelines for the safe reuse of human excreta in agriculture (WHO 2006).

Other innovations in the area of ecological sanitation have significantly increased the feasibility of extracting phosphorus from municipal wastewater streams (Gantenbein and Khadka 2009, Tilley et al. 2009). The output is the mineral struvite, a white solid formed when bacteria are used to clean up sludge. Struvite has demonstrated value as a source of phosphorus-based fertilizer (Johnston and Richards 2003). First used commercially in 2007, this technology is currently in full-scale use in treatment plants in some major cities in North America and the United Kingdom.

During the past decade, researchers have started to focus on reducing phosphorus losses by developing ways to improve phosphorus uptake by animals. In particular, intensive pig rearing produces massive volumes of phosphorus-rich manure. Monogastric animals such as the pig are unable to break down phytate, the major form of phosphorus in their feed. Phosphorus is therefore added to their diet as an inorganic supplement, but much of it is excreted due to low uptake in the gut. Scientists at the University of Guelph in Canada have developed a genetically engineered

Box 5: From waste to phosphorus recovery and recyclingEnviropig able to digest phytate (Forsberg et al. 2003). This decreases the need for an inorganic phosphorus supplement. Other research groups are developing low-phytate crops or focusing on the production of phytase, an enzyme that helps animals to digest phytate.

UNEP YEAR BOOK 201144

Populationgrowthandeconomicdevelopmentareexpectedtofurtherincreaseagriculturalproduction,particularlylivestockraising.Futuredemandforphosphoruswillstronglydependonthetypesofagriculturalpracticesthataccompanythisincrease(Vitousek et al. 2009). Dietary changes and reduction of foodwaste in the retail sector and households would help reducephosphorus losses, and would require greater awareness andachangeinattitudeinordertoalterconsumptionpatterns.Aspromising options emerge, they will call for decision makingbased on reliable scientific evidence derived from furtherresearchonphosphorusavailability,productflowsandend­uses(Hiltonetal.2010,VanVuurenetal.2010).

Looking aheadPhosphorus has received only limited attention compared tootherimportantagriculturalinputssuchasnitrogenandwater.Becauseofthevitalroleofphosphorusinfoodproduction,anyconsideration of food security needs to include an informeddiscussion concerning more sustainable use of this limitedresource.Keythemesincludetheincreasingglobaldemandforphosphorus fertilizers, theongoingdebateover the long­termavailability of phosphate rock, lack of adequate phosphorusaccessibility by many of the world’s farmers, prospects forincreased recycling and more efficient phosphorus use inagriculture, and minimization of losses through soil erosion

control. More detailed research is required to provide reliable,global­scale quantification of the amount of phosphorusavailableforfoodproduction.Aglobalphosphorusassessment,including further insights from scientists and other experts,policy­makers and other stakeholders, could contribute toimproving fertilizer accessibility, waste management in urbansettings,andrecyclingofphosphorusfromfoodwasteandfromanimalandhumanexcreta.

The long­term availability of phosphorus for global foodproductionisoffundamentalimportancetotheworldpopulation.Given the diversity of issues surrounding phosphorus, only anintegrated set of policy options and technical measures canensureitsefficientandsustainableuse.Environmentalsolutionsthat improve nutrient management and recycling, minimizephosphorus losses due to soil erosion, and foster sustainableproductionandconsumptionalsopromotewiseuseofafiniteresource. This could be the basis for fostering environmentalinnovation and other actions at local, national, regional andinternational levels to improve phosphorus management.Thefuture of this resource will also depend on governance withregardtoitsextractionanddistributionaroundtheworld.Thereis a need for accurate information about the extent of globalreserves,newtechnologies,infrastructure,institutions,attitudesand policies to meet the challenge of sustainably feeding arapidlygrowingglobalpopulationwhilemaintainingahealthyandproductiveenvironment.

Scrubbing and washing with seawater of phosphate rock in the coastal area of Togo. Credit: Takehiro Nakamura

45PHOSPHORUS AND FOOD PRODUCTION

ReferencesAfrica Fertilizer Summit (2006). Africa Fertilizer Summit Proceedings. International Fertilizer Development Center (IFDC), Muscle Shoals, Alabama, USAAlley, M.M. and Vanlauwe, B. (2009). The Role of Fertilizers in Integrated Plant Nutrient Management. International Fertilizer Industry Association (IFA), Paris, and Tropical Soil Biology and Fertility Institute of the International Centre for Tropical Agriculture (TSBF-CIAT), NairobiBennett, E.M., Carpenter, S.R. and Caraco, N.F. (2001). Human impact on erodable phosphorus and eutrophication: A global perspective. Bioscience, 51(3), 227-234Buresh, R.J., Smithson, P.C. and Heliums, D.T. (1997). Building Soil Phosphorus Capital in Africa. In: Buresh, R.J., Sanchez, P.A. and Calhoun, F. (eds.), Replenishing Soil Fertility in Africa. Special Publication No. 51. Soil Science Society of America (SSSA) and American Society of Agronomy (ASA), Madison, Wisconsin, USACarpenter, S.R., Caraco, N.F., Correll, D.L., Howarth, R.W., Sharpley, A.N. and Smith, V.H. (1998). Nonpoint pollution of surface waters with phosphorus and nitrogen. Ecological Applications, 8(3), 559-568 Cordell, D., Drangert, J.-O. and White, S. (2009). The Story of Phosphorus: Global food security and food for thought. Global Environmental Change, 19, 292-305Dagerskog, L. and Bonzi, M. (2010). Opening minds and closing loops – productive sanitation initiatives in Burkina Faso and Niger. Sustainable Sanitation Practice, 3 Dodds, W.K., Bouska, W.W., Eitzmann, J.L., Pilger, T.J., Pitts, K.L., Riley, A.J. and Thornbrugh, D.J. (2009). Eutrophication of US Freshwaters: Analysis of Potential Economic Damages. Environmental Science & Technology, 43(1), 12-19Drecht, G. van, Bouwman, A.F., Harrison, J. and Knoop, J.M. (2009). Global nitrogen and phosphate in urban wastewater for the period 1970 to 2050. Global Biogeochemical Cycles, 23Drummond, A. (2010). Minemakers: Targeting Phosphate Production from Two Continents. Paper presented at the Phosphates 2010 International Conference, 22-24 March, Brussels El-Swaify, S.A., Dangler, E.W. and Armstrong, C.L. (1982). Soil erosion by water in the tropics. Research Extension Series 024, College of Tropical Agriculture and Human Resources, University of HawaiiEsrey, S., Andersson, I., Hillers, A. and Sawyer, R. (2001). Closing the Loop: Ecological sanitation for food security. Publication on Water Resources No. 18. United Nations Development Programme (UNDP) and Swedish International Development Cooperation Agency (SIDA)FAO (2008). Soaring food prices: facts, perspectives, impacts and actions required. Presented at the High-level Conference on World Food Security: The Challenges of Climate Change and Bioenergy, 3-5 June 2008, Food and Agriculture Organization of the United Nations, RomeFAO (2010). The State of Food Insecurity in the World 2010: Addressing food insecurity in protracted crises. Food and Agriculture Organization of the United Nations, RomeFAOStat (2009). Online database providing time-series and cross sectional data relating to food and agriculture for some 200 countries. Food and Agriculture Organization of the United Nations, Rome. http://faostat.fao.orgForsberg, C.W., Phillips, J.P., Golovan, S.P., Fan, M.Z., Meidinger, R.G., Ajakaiye, A., Hilborn, D. and Hacker, R.R. (2003). The Enviropig physiology, performance, and contribution to nutrient management advances in a regulated environment: The leading edge of change in the pork industry. Journal of Animal Science, 81, 68-77Fresco, L. (2009). Challenges for food system adaptation today and tomorrow. Environmental Science & Policy, 12, 2009, 378-385Gantenbein, B. and Khadka, R. (2009). Struvite Recovery from Urine at Community Scale in Nepal. Final Project Report Phase I. Swiss Federal Institute of Aquatic Science and Technology (Eawag), Duebendorf, Switzerland, and UN-Habitat Water for Asian Cities Programme Nepal, Kathmandu Gilbert, N. (2009). The disappearing nutrient. Nature, 461, 716-718GPNM (2010). Building the foundations for sustainable nutrient management. A publication of the Global Partnership on Nutrient Management. Published by the United Nations Environment Programme on behalf of the Global Partnership on Nutrient Management

Heffer, P. and Prud’homme, M. (2010). Fertilizer Outlook 2010-2014, 78th IFA Annual Conference, 31 May-2 June 2010, International Fertilizer Industry Association (IFA), ParisHenao, J. and Baanante, C. (2006). Agricultural Production and Soil Nutrient Mining in Africa: Implications for Resource Conservation and Policy Development. International Fertilizer Development Center (IFDC), Muscle Shoals, Alabama, USAHilton, J., Johnston, A.E. and Dawson, C.J. (2010). The Phosphate Life-Cycle: Rethinking the Options for a Finite Resource. Proceedings No. 668. International Fertiliser Society, Leek, UKIAASTD (2009). Agriculture at a Crossroads: Synthesis Report. International Assessment of Knowledge, Science and Technology for DevelopmentIFA (2006). Production and International Trade Statistics. International Fertilizer Industry Association, ParisIFA (2008). Feeding the Earth: Fertilizers and Global Food Security, Market Drivers and Fertilizer Economics. International Fertilizer Industry Association, ParisIFA (2009). Annual Phosphate Rock Statistics. International Fertilizer Industry Association, ParisIFDC/UNIDO (1998). Fertilizer Manual. Prepared by the International Fertilizer Development Center (IFDC) and the United Nations Industrial Development Organization (UNIDO). Kluwer Academic Publishers, Dordrecht, the NetherlandsIFPRI (2002). GREEN REVOLUTION: Curse or Blessing? International Food Policy Research Institute, Washington, D.C.Jacob, K.D. (1964). Predecessors of superphosphate. In: United States Department of Agriculture and Tennessee Valley Authority (TVA), Superphosphate: Its history, chemistry and manufacture. United States Government Printing Office, Washington, D.C.Jasinski, S.M. (2006). Phosphate Rock. In: Mineral Commodity Summaries 2006. United States Geological Survey. United States Government Printing Office, Washington, D.C.Jasinski, S.M. (2007). Phosphate Rock. In: Mineral Commodity Summaries 2007. United States Geological Survey. United States Government Printing Office, Washington, D.C.Jasinski, S.M. (2008). Phosphate Rock. In: Mineral Commodity Summaries 2008. United States Geological Survey. United States Government Printing Office, Washington, D.C.Jasinski, S.M. (2010). Phosphate Rock. In: Mineral Commodity Summaries 2010. United States Geological Survey. United States Government Printing Office, Washington, D.C.Jasinski, S.M. (2011). Phosphate Rock. In: Mineral Commodity Summaries 2011. United States Geological Survey. United States Government Printing Office, Washington, D.C. Johnston, A.E. and Richards, I.R. (2003). Effectiveness of different precipitated phosphates as phosphorus sources for plants. Soil Use and Management, 19, 45-49Jung, A. (2010). Phosphates Fertilizer Outlook, British Sulphur Consultants. Paper presented at the Phosphates 2010 International Conference, 22-24 March, 2010, BrusselsKauwenbergh, S. Van. (2010). World Phosphate Rock Reserves and Resources, IFDC Technical Bulletin 75. International Fertilizer Development Center (IFDC), Muscle Shoals, Alabama, USAMA (2005). Nutrient Cycling. Chapter 12 in: Hassan, R., Scholes, R. and Ash, N. (eds.), Ecosystems and Human Well-Being: Current State and Trends, Volume 1. Millennium Ecosystem Assessment. Island Press, Washington, D.C.Morgan, P. (2007). Toilets That Make Compost: Low-cost, sanitary toilets that produce valuable compost for crops in an African context. Stockholm Environment InstituteNyenje, P.M., Foppen, J.W., Uhlenbrook, S., Kulabako, R. and Muwanga, A. (2010). Eutrophication and nutrient release in urban areas of sub-Saharan Africa – A review. Science of the Total Environment, 408(3), 447-455Prud’homme, M. (2010). World Phosphate Rock Flows, Losses and Uses. Paper presented at the Phosphates 2010 Conference and Exhibition, Brussels, March 2010

Rockström, J., Steffen, W., Noone, K., Persson, A., Chapin, F.S., Lambin, E.F. and Foley, J.A. (2009). A safe operating space for humanity. Nature, 461(7263), 472-475Rosemarin, A., Ekane, N., Caldwell, I., Kvarnström, E., McConville, J., Ruben, C. and Fogde, M. (2008). Pathways for Sustainable Sanitation: Achieving the Millennium Development Goals. Stockholm Environment Institute. IWA Publishing, LondonSchröder, J.J., Cordell, D., Smit, A.L. and Rosemarin, R. (2010). Sustainable Use of Phosphorous. Report No. 357. Plant Research International, Wageningen University and Research Centre, the Netherlands, and Stockholm Environment InstituteSharpley, A. and Rekolainen, S. (1997). Phosphorus in Agriculture and Its Environmental Implications. In: Tunney, H., Carton, O.T., Brookes, P.C. and Johnston, A.E. (eds.), Phosphorus Loss from Soil to Water. CAB International, Wallingford, UK Smaling, E.M.A., Nandwa, S.M. and Janssen, B.H. (1997). Soil fertility in Africa is at stake. In: Buresh, R.J., Sanchez, P.A. and Calhoun, F. (eds.), Replenishing Soil Fertility in Africa. Special Publication No. 51. Soil Science Society of America (SSSA) and American Society of Agronomy, Madison, Wisconsin, USASmil, V. (2000). Phosphorus in the Environment: Natural Flows and Human Interferences. Annual Review of Energy and the Environment, 25, 53-88Smil, V. (2002). Phosphorus: Global Transfers. In: Douglas, I. (ed.), Encyclopedia of Global Environmental Change, Volume 3, Causes and Consequences of Global Environmental Change. John Wiley & Sons, Chichester, UKStocking, M. (1984). Rates of erosion and sediment yield in the African environment. In: Walling, D.E., Foster, S.S.D. and Wurzel, P. (eds.), Challenges in African Hydrology and Water Resources (Proceedings of the Harare Workshop Symposium in July 1984). International Association of Hydrological Sciences (IAHS) Publication No. 14Swedish Environmental Protection Agency (2010). Reporting of government assignment 21: Update of the “Action Plan for Reuse of Phosphorus from Wastewater”. Ministry of Environment, StockholmSyers, J.K., Johnston, A.E. and Curtin, D.C. (2008). Efficiency of Soil and Fertilizer Phosphorus Use. FAO Fertilizer and Plant Nutrition Bulletin 18Tilley. E., Gantenbein, B., Khadka, R., Zurbrügg, C. and Udert, K.M. (2009). Social and Economic Feasibility of Struvite Recovery from Urine at the Community Level in Nepal. In: Ashley, K., Mavinic, D. and Koch, F. (eds.), International Conference on Nutrient Recovery from Wastewater Streams. IWA Publishing, LondonUN (2009). World Population Prospects: The 2008 Revision. Highlights. Population Division of the Department of Economic and Social Affairs of the United Nations Secretariat, United Nations, New YorkUN (2010). The Millennium Development Goals Report. United Nations Department of Economic and Social Affairs, United Nations, New York2008UNEP/IFA (2001). Environmental Aspects of Phosphate and Potash Mining. United Nations Environment Programme and International Fertilizer Industry Association (IFA), ParisUNGA (2010). Keeping the promise: United to achieve the MDGs. A forward-looking review to promote an agreed action agenda to achieve the Millennium Development Goals by 2015. United Nations General Assembly 64/665Vaccari, D.A. (2009). Phosphorus Famine: The Threat to Our Food Supply. Scientific American, June, 54-59Vitousek, P.M., Naylor, R., Crews, T., David, M.B., Drinkwater, L.E., Holland, E., Johnes, P.J., Katzenberger, J., Martinelli, L.A., Matson, P.A., Nziguheba, G., Ojima, D., Palm, C.A., Robertson, G.P., Sanchez, P.A., Townsend, A.R. and Zhang, F.S. (2009). Nutrient imbalances in agricultural development. Science 324(5934), 1519-1520Vuuren, D.P. Van, Bouwman, A.F. and Beusen, A.H.W. (2010) Phosphorus demand for the 1970-2100 period: A scenario analysis of resource depletion. Global Environmental Change, 20, 428-439WHO (2006). Guidelines for the safe use of wastewater, excreta and greywater. Volume 4: Excreta and greywater use in agriculture. World Health Organization, Geneva